public class Task {

    public static void main(String[] args) {
        int[] arr = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71};

        int rst = binarySearch(arr, 31);

        System.out.println(rst);
    }

    // 二分查找算法
    public static int binarySearch(int[] arr, int target) {
        return -1;
    }

}